Select Random columns from a matrix as a signal in Simulink

I have a matrix 360x9 in a from workspace block. By specifying a constant block with a value n, I would like to output n columns randomly selected from the data as an output and plot them on a scope. I have tried utilizing a MATLAB function block and using the following code

function y = fcn(u, data)
ncol=u
s=randi(size(data,2),1,ncol);
y=data(:,s)
end

This logic works in matlab alone, however when implemented into a MATLAB function block I recieve an error stating that y is inferred as a variable-size matrix and must be defined in terms of non-tunable parameters or specify variable size. If I specify variable size in the model explorer, the output signal has a nondiscrete sample time, and it must be discrete. Any help would be greatly appreciated. Thanks.

Answer 1

[Fangjun Jiang]

1. The number of columns "u" comes from an input of the MATLAB Function block, so the data involved IS variable size.
2. The MATLAB Function block is executed once at every simulation step. Are you sure this is what you want?
3. A better approach is to process this randomness as initialization and then input the processed data into Simulink.

[Nicholas Lindenfeldar]

Thanks, I didn't think of that. I was able to implement it as an initialization script.